In Rel-10 of a long-term evolution advanced (LTE-A) system, in order to provide a higher transmission rate to terminal, a carrier aggregation technology is introduced and 5 deployment scenarios of the carrier aggregation technology are defined. However, in the Rel-10, for an uplink, intra-band carrier aggregation is only supported. And at the same time, for scenarios 4 and 5, that is, scenarios where receiving stations of uplink signals of different carriers are different, an uplink carrier aggregation technology is not supported. In LTE-A Rel-11, the carrier aggregation technology is further enhanced, with one aspect of enhancement being that for an uplink, carrier aggregation in different bands is supported, and uplink carrier aggregation being supported in scenarios 4 and 5.
When timing advance of an uplink signal of a secondary serving cell configured for terminal is different from that of a timing advance group (TAG) where the secondary serving cell is present, the secondary serving cell needs to be reconfigured to a correct TAG. FIG. 1 is a schematic diagram of needing to reconfigure a TAG. In this figure, an eNB configures terminal with a primary serving cell f1 and a secondary serving cell f2, both of them belonging to the same band.
A first case: the terminal is located at A point at a moment T1, when receiving stations of the secondary serving cell (Scell) and the primary serving cell (Pcell) are identical, which are eNBs; hence, they belong to the same TAG, which is defined as a pTAG (i.e. a TAG where a Pcell is present). At a moment T2, the terminal moves to a coverage (such as point B) of a repeater, when a receiving station of uplink signals in the Scell is changed into the repeater, which is different from a receiving station of the Pcell. Hence, the Scell is no longer suitable to belonging to the same TAG as that of the Pcell, and needs to be reconfigured to a new TAG, which is defined as a sTAG (i.e. a TAG where there exists a Scell only).
A second case: contrary to the first case, the terminal moves from the coverage of the repeater to the coverage of the eNB. In such a case, the Scell of the terminal needs to be reconfigured from the sTAG to the pTAG.
For the above second case, after the Scell is reconfigured to the pTAG, as a timing advance (TA) value of the pTAG is known, after the reconfiguration process is completed, the terminal may transmit an uplink signal in the Scell immediately. While for the first case, after the Scell is reconfigured to a new sTAG, as an uplink TA value of the new sTAG is unknown, after the reconfiguration process is completed, the terminal needs to execute a random access process in the Scell to obtain an initial TA value of the sTAG. However, in the process of obtaining the TA value of the sTAG by the terminal, if the terminal transmits an uplink signal in the Scell according to the TA value of the pTAG, as the TA value cannot ensure that the time when the uplink signal of the terminal reaches the repeater and those of other terminals are synchronous, it possibly results in mutual interference with other terminals.
It should be noted that the above description of the background art is merely provided for clear and complete explanation of the present application and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background art of the present application.